Japanese Foxtail (Alopecurus japonicus) is a monocot weed in the Poaceae family. In China this weed first evolved resistance to Group A/1 herbicides in 2007 and infests Canola, and Winter wheat. Group A/1 herbicides are known as ACCase inhibitors (Inhibition of acetyl CoA carboxylase (ACCase)). Research has shown that these particular biotypes are resistant to clodinafop-propargyl, fenoxaprop-P-ethyl, haloxyfop-methyl, and pinoxaden and they may be cross-resistant to other Group A/1 herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

Field, Greenhouse, and Laboratory trials comparing a known susceptible Japanese Foxtail biotype with this Japanese Foxtail biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on Group A/1 resistant Japanese Foxtail indicate that the inheritance is determined by a one gene, dominant trait. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

Studies on the mechanism of resistance of Group A/1 resistant Japanese Foxtail from China indicate that resistance is due to an altered target site. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group A/1 resistant Japanese Foxtail from China please update the database.

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in China have been instrumental in providing you this information. Particular thanks is given to Liyao Dong, Li Jun, and Jinxin Wang for providing detailed information.

BACKGROUND: Haloxyfop-R-methyl is a widely used herbicide to control Poaceae weeds. Alopecurus japonicus, a widespread annual grass, can no longer be controlled by haloxyfop-R-methyl after continuous use of this herbicide for several years. RESULTS: Dose-response experiments have established that the Js-R biotype of A. japonicas has evolved resistance to aryloxyphenoxypropionates (APPs). Target-site enzyme sensitivity experiments have established that the haloxyfop (free acid) rate causing 50% inhibition of acetyl-CoA carboxylase (ACCase) activity (I50) for the resistant (Js-R) biotype is 11 times higher than that for the susceptible (Js-S) biotype. In many cases, resistance to ACCase-inhibiting herbicides is due to a resistant ACCase enzyme. Full-length DNA and mRNA sequences of the plastidic ACCase gene were amplified. Eight single-nucleotide differences were detected in this region. Four of the nucleotide changes were silent mutations. However, the other four nucleotide mutations caused four amino acid substitutions, replacing Arg-1734 with Gly, Met-1738 with Leu, Thr-1739 with Ser and Ile-2041 with Asn in the R biotype respectively; the substitution at position 2041 had been reported, while the other three had not. CONCLUSION: The ACCase in the Js-R biotype was less susceptible to haloxyfop-R-methyl than that in the Js-S biotype. Moreover, the amino acid substitution of Ile-2041 with Asn might confer resistance to haloxyfop-R-methyl in A. japonicas..

Japanese foxtail is one of the most common and troublesome weeds infesting cereal and oilseed rape fields in China. Repeated use during the last three decades of the ACCase-inhibiting herbicide fenoxaprop-P-ethyl to control this weed has resulted in the occurrence of resistance. Dose-response tests established that a population (AHFD-1) from eastern China had evolved high-level resistance to fenoxaprop-P-ethyl. Based on the resistance index, this resistant population of A. japonicus is 60.31-fold resistant to fenoxaprop-P-ethyl. Subsequently, only a tryptophan to cysteine substitution was identified to confer resistance to fenoxaprop-P-ethyl in this resistant population. ACCase activity tests further confirmed this substitution was linked to resistance. This is the first report of the occurrence of Trp-2027-Cys substitution of ACCase in A. japonicus. From whole-plant pot dose-response tests, we confirmed that this population conferred resistance to other APP herbicides, including clodinafop-propargyl, fluazifop-P-butyl, quizalofop-P-ethyl, haloxyfop-R-methyl, cyhalofop-butyl, metamifop, DEN herbicide pinoxaden, but not to CHD herbicides clethodim, sethoxydim. There was also no resistance observed to ALS-inhibiting herbicides sulfosulfuron, mesosulfuron-methyl, flucarbazone-sodium, pyroxsulam, Triazine herbicide prometryne and glyphosate. However, this resistant population was likely to confer slightly (or no) resistant to Urea herbicides chlortoluron and isoproturon..

BACKGROUND: Haloxyfop-R-methyl is a widely used herbicide to control Poaceae weeds. Alopecurus japonicus, a widespread annual grass, can no longer be controlled by haloxyfop-R-methyl after continuous use of this herbicide for several years. RESULTS: Dose-response experiments have established that the Js-R biotype of A. japonicas has evolved resistance to aryloxyphenoxypropionates (APPs). Target-site enzyme sensitivity experiments have established that the haloxyfop (free acid) rate causing 50% inhibition of acetyl-CoA carboxylase (ACCase) activity (I50) for the resistant (Js-R) biotype is 11 times higher than that for the susceptible (Js-S) biotype. In many cases, resistance to ACCase-inhibiting herbicides is due to a resistant ACCase enzyme. Full-length DNA and mRNA sequences of the plastidic ACCase gene were amplified. Eight single-nucleotide differences were detected in this region. Four of the nucleotide changes were silent mutations. However, the other four nucleotide mutations caused four amino acid substitutions, replacing Arg-1734 with Gly, Met-1738 with Leu, Thr-1739 with Ser and Ile-2041 with Asn in the R biotype respectively; the substitution at position 2041 had been reported, while the other three had not. CONCLUSION: The ACCase in the Js-R biotype was less susceptible to haloxyfop-R-methyl than that in the Js-S biotype. Moreover, the amino acid substitution of Ile-2041 with Asn might confer resistance to haloxyfop-R-methyl in A. japonicas..

Japanese foxtail is one of the most common and competitive annual grass weeds of wheat in China. Whole-plant dose-response experiments were conducted with fenoxaprop and pinoxaden to confirm and characterize resistant and susceptible Japanese foxtail populations and to elucidate the basis of resistance to these herbicides. The resistant Japanese foxtail population was 49-fold resistant to fenoxaprop and 16-fold (cross) resistant to pinoxaden relative to the susceptible population, which was susceptible to both fenoxaprop and pinoxaden herbicides. Molecular analysis of resistance confirmed that the Ile1781 to Leu mutation in the resistant population conferred resistance to both fenoxaprop and pinoxaden. This is the first report of cross resistance of Japanese foxtail to pinoxaden in the world and of a target site mutation that corresponded to resistance to both fenoxaprop and pinoxaden in Japanese foxtail. Prior selection pressure from fenoxaprop could result in evolution of resistance to fenoxaprop and cross resistance to pinoxaden in Japanese foxtail population..

The North China Plain (NCP) is one of the most important winter wheat production areas in the world. A double cropping system of winter wheat followed by summer maize in one year is the most common cropping practice in the NCP. However new crops and agricultural practices including chemical weed control measures were recently introduced in this area. Alopecurus spp., Aegilops squarrosa L. and Bromus japonicus Thunb. were found to be the most abundant grass weeds in the NCP winter wheat production system. In 2008 and 2009, A. japonicus seeds were collected from different locations in the NCP to conduct herbicide efficacy studies. Besides conventional glasshouse bioassays a rapid herbicide resistance test has been developed and tested. This new resistance test is based on chlorophyll fluorescence microscreenings for evaluation of the efficacy of herbicides on grass weeds grown in tissue culture plates filled with an agar-herbicide solution. In glasshouse bioassays for chlorotoluron a resistance factor of 3.5 was found for one of the NCP biotypes compared to the sensitive control biotype. The chlorophyll fluorescence microscreening clearly verified this result. Further studies showed that this method is also suitable for other herbicide modes of action like ALS and ACC inhibitors. Furthermore this method is easily transferable to other important grass weeds. Using the chlorophyll fluorescence assay, it becomes possible to evaluate efficacy for a large number of biotypes with a minimum requirement of time and space. Therefore it is well suited for high throughput resistance screenings, especially at locations where glasshouse space is a limiting factor. An accelerated identification of resistant grass weed biotypes and thus a prompt resistance management plan for the field will be of great importance for the North China Plain and other intensive agricultural areas in the world..

The North China Plain (NCP) is one of the most important winter wheat production areas in the world. A double cropping system of winter wheat followed by summer maize in one year is the most common cropping practice in the NCP. However new crops and agricultural practices including chemical weed control measures were recently introduced in this area. Alopecurus spp., Aegilops squarrosa L. and Bromus japonicus Thunb. were found to be the most abundant grass weeds in the NCP winter wheat production system. In 2008 and 2009, A. japonicus seeds were collected from different locations in the NCP to conduct herbicide efficacy studies. Besides conventional glasshouse bioassays a rapid herbicide resistance test has been developed and tested. This new resistance test is based on chlorophyll fluorescence microscreenings for evaluation of the efficacy of herbicides on grass weeds grown in tissue culture plates filled with an agar-herbicide solution. In glasshouse bioassays for chlorotoluron a resistance factor of 3.5 was found for one of the NCP biotypes compared to the sensitive control biotype. The chlorophyll fluorescence microscreening clearly verified this result. Further studies showed that this method is also suitable for other herbicide modes of action like ALS and ACC inhibitors. Furthermore this method is easily transferable to other important grass weeds. Using the chlorophyll fluorescence assay, it becomes possible to evaluate efficacy for a large number of biotypes with a minimum requirement of time and space. Therefore it is well suited for high throughput resistance screenings, especially at locations where glasshouse space is a limiting factor. An accelerated identification of resistant grass weed biotypes and thus a prompt resistance management plan for the field will be of great importance for the North China Plain and other intensive agricultural areas in the world..